To cross transmission lines for high frequency signals it is known to provide a circuit substrate having multiple metallization layers, on which transmission lines, developed in different metallization layers, can cross each other. For this purpose, a transmission line in a metallization layer can bridge a crossing area by a detour via a different metallization layer. A disadvantage in this instance is the additional effort for providing a second or more metallization layers.
It is also known to realize a crossing of two transmission lines of the same metallization layer via a bridge made up of a discrete component. Depending on the requirements, however, disadvantageous output losses can result.
In “Microstrip EHF Butler Matrix Design and Realization”, ETRI Journal, Volume 27, No. 6, December 2005, J.-S. Néron and G.-Y. Delisle describe a coupling structure for crossing two transmission lines for a 36 GHz signal. The coupling structure is made up of a planar cross-coupler, also known as a 0-dB coupler, that enables crossing two transmission lines having minimal coupling between them. The planar cross-coupler is embodied as a cascade of two 90 degree hybrid couplers. From an input signal at one of two input points, such a 90 degree hybrid coupler, known per se, generates two signals phase-shifted by 90 degrees, at its output points.